Impact of low rainfall during dormancy on vine productivity and development.

Background and Aims: Declining autumn and winter rainfall increasingly limits soil moisture availability at the onset of the growing season in southern Australia. We studied the consequences of reduced rainfall during dormancy on vine growth, and explored irrigation strategies to maintain yield following dry winters. Methods and Results: The effect of the timing and method of irrigation during dormancy on vine performance was investigated for three seasons in a Shiraz vineyard where late autumn and winter rainfall was excluded using shelters. Reduced soil moisture in spring delayed the time of budburst. A reduction in rain to approximately one third of the historical average reduced yield (24–42%) and canopy size (16–31%). Natural rain (Control) or equivalent sprinkler irrigation, providing water during winter, resulted in a higher yield: pruning mass ratio, but reduction in yield was still observed when drip irrigation was used to replace winter rain. Refilling the soil profile in spring after dry winters favoured growth partitioning towards canopy and roots, increased carbohydrate reserves in the trunk, but reduced yield (−10 to −32%). Conclusions: Irrigation during winter did not fully offset the decline in production. Refilling the soil profile at the end of winter increased vigour, and reduced yield. Reduced soil moisture prior to spring delayed the time of budburst. Significance of the Study: Vineyard management aiming to sustain yield under a changing climate will need to incorporate winter irrigation. Models predicting the time of budburst under a changing environment could be fine‐tuned by incorporating soil moisture availability. [ABSTRACT FROM AUTHOR]